Estrogen effects on prolactin synthesis are being studied in cell cultures as well as in vivo. We plan to try and determine whether the increases in prolactin synthesis are a function of increased cell numbers or increased prolactin production per cell. Closely tied to this is the investigation of whether inhibitors of cell replication will block the estrogen effects. We have shown that estrogen brings about increases in preprolactin mRNA accumulation. We would like to determine if this is due to increase in mRNA synthesis or processing. We are also trying to establish procedures for enriching the prolactin producing cells in our primary cell cultures. Affinity binding procedures as well as variations in culture procedures will be used.